Chemistry calculations become much easier when students slow down, track units, and know which relationship they are using.
Forgetting to convert units
Students often lose marks by mixing grams, kilograms, centimetres cubed, and decimetres cubed. Before calculating, check whether the equation expects a particular unit.
Using the wrong ratio
Balanced equations give the mole ratio. If students ignore the coefficients, they may calculate the correct number for the wrong substance relationship.
Rounding too early
Rounding halfway through a calculation can shift the final answer. It is usually better to keep extra digits during working and round only at the end.
Not writing the formula first
Writing the formula gives structure and can earn method marks. For example, using moles equals mass divided by Mr makes it clear what the student is trying to calculate before substituting values.